Poly Reducer issues in Blender 2.71
The decimate modifier is the closet alternative. I find Un-subdivide to be the best(using even numbers of iterations generally creates better results), the other methods are good to, just try all of them for the best results. 

Note, in Blender 2.4x the decimator didn't support UV's, vertex groups and it triangulated everything, however the decimator now supports these - so there is no need for the script.